Benefit Obligation, Amounts Recognized Company's Financial Statements and Principal Assumptions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in projected benefit obligation:
Benefit obligation at beginning of year	$ 4,218	$ 3,419
Service cost		101	$ 387
Interest cost	114	111	98
Actuarial (gain) loss	(158)	78
Prior service cost	(342)	509
Benefit obligation at end of year	3,832	4,218	3,419
Gentherm GmbH
Change in projected benefit obligation:
Benefit obligation at beginning of year	7,927	7,326
Interest cost	147	130	154
Paid pension distributions	(292)	(272)
Actuarial (gain) loss	114	(257)
Exchange rate impact	(367)	1,000
Benefit obligation at end of year	$ 7,529	$ 7,927	$ 7,326